1. Field of the Invention
The present invention relates to a liquid ejection apparatus and a liquid ejection method using the liquid ejection apparatus. More particularly, the invention relates to a liquid ejection apparatus and a liquid ejection method for ejecting liquid inside a tank into a space above the liquid surface, or towards a peripheral wall.
2. Description of the Related Art
In fermentation and culturing, the fermenting liquids and culturing liquids are very prone to foaming. Due to agitation during the process, there is a considerable amount of foaming so that operability is often impaired. In order to inhibit such foaming, and to disperse the temporarily created foam, anti-foaming agents such as silicone are added. The addition of such anti-foaming agents however not only involves significant cost, but also poses a risk adversely affecting the fermentation and culturing processes, because these anti-foaming agents are in themselves foreign substances to the liquids. In addition, the anti-foaming agents are mixed with the product as impurities so that the quality of the product is degraded. Moreover additional time is required to remove them from the product. Furthermore they are mixed in the waste liquid and thus impede the treatment of the waste liquid. Hence the addition of anti-foaming agents is an undesirable means, which should be avoided as much as possible.
A problem is that the inner peripheral surface of the wall of the agitating tank becomes contaminated by micro-organisms or solid raw materials or products being deposited thereon. This often causes a decrease in reaction yield or a reduction in heat transfer coefficient of the agitating tank peripheral wall. In this case, it is practically impossible to wash the inner peripheral surface of the wall of the agitating tank to remove the extraneous matter from the inner peripheral surface of the agitating tank without stopping the operation in the agitating tank.
Yet another problem is that when apparatus such as jackets, and coiled pipes and multi-tube heating units are respectively provided on the outer peripheral surface of the peripheral wall of the agitating tank and inside the agitating tank, as apparatus for heating or cooling the liquid inside the agitating tank, there is often the situation where the liquid inside the agitating tank decreases due for example to evaporation so that with time, the liquid level inside the agitating tank drops, and the heat transfer area of the heating or cooling apparatus cannot be effectively utilized.
In order to increase and hence recover the reduced heat transfer area, there is a means involving supplying fresh liquid to the tank so that the liquid surface is raised; and a method involving circulating the remaining liquid inside the tank by means of a pump provided outside of the tank to distribute the liquid onto the inner peripheral surface of the tank wall. The former wherein fresh liquid is supplied to the tank, has the defect that there is an abrupt change in the composition of the liquid inside the tank, requiring a change in operational conditions, and also the quality of the product changes. Moreover, the latter has the defect that it requires a pump and piping for circulating the remaining liquid, so that after operation, residual liquid remains in the tank as well as inside the piping.
Accordingly, means which can be put into practice to solve the defect that the heat transfer area cannot be effectively used have yet to be found.
When desired to evaporate the liquid inside the agitating tank, there is a method involving immersing a heating device in the liquid and/or mounting a heating device on the outside of the agitating tank peripheral wall, to thereby apply heat to cause evaporation from the liquid surface either while agitating or not agitating the liquid. With this method there is the defect that the heat in the space above the liquid surface which is heated by the heating device cannot be effectively utilized, and that the heating of the liquid is limited to the contact area of the heating device, so that the heat from the heating device cannot be effectively utilized and the rate of evaporation of the liquid is slow.
The present inventors have overcome the defects with the conventional agitation such as contamination of the surface of the inner peripheral surface of the peripheral wall of the agitating tank and the surface of the heating or cooling apparatus and a reduction in the heat transfer area by using only mechanical agitation. Hence, with good efficiency, the inner peripheral surface of the peripheral wall of the agitating tank and the surface of the heating or cooling apparatus are washed, thereby preventing the reduction in the heat transfer area of the inner peripheral surface of the peripheral wall of the agitating tank and of the heating or cooling apparatus. Moreover, the accumulated results of a thorough study into agitating blades and agitating methods which can achieve mixing of liquids of different specific gravities and suspensions with good efficiency, have led to an invention related to agitating blades and agitating methods (EP 0619136A).
The agitating blades of this prior invention are agitating blades wherein a liquid transporting body such as one or a plurality of tubular bodies, gutter bodies, and plates, is attached preferably at an incline to an attachment device mounted on an agitator shaft, the liquid transporting body being open at both ends with an upper opening and lower opening.
The present inventors, from the accumulated results of continuous investigations to solve the former problems discovered the following problems in the invention related to the beforementioned patent application. That is to say, in the abovementioned prior application, the liquid transporting body is preferably secured at an incline. Since the inclination angle is fixed and is not changed, then in changing the purpose of use and the conditions of the agitating blades, the agitating blades must be stopped and removed from the tank to change the inclination angle.
Furthermore, with the tubular body constituting the liquid transporting body, normally it is common for this to be in contact with liquids with strong corrosive characteristics. Hence in order to have complete corrosion resistance, the surface is coated or lined with a substance having a high corrosion resistance such as a synthetic resin like polytetrafluoroethylene, or glass or a ceramic or the like. However, while with such a coating or lining, the technology has improved remarkably, there is still the danger of pinholes. Consequently due to these pinholes, it is difficult to ensure the reliability of the corrosion resistance of the coated or lined tubular body.
In order to increase the reliability of the corrosion resistance of the tubular body, then prior to use of the tubular body, the presence of pinholes in the coating layer or the lining layer of the tubular body (these layers are in general referred to simply as a lining layers) is preferably checked for not only on the outer face of the pipe but also on the inner face. However, checking for the presence of pinholes in the inner face of the pipe is extremely difficult. Moreover, even if pinholes are found, it is difficult to repair these pinholes.
Therefore it is preferable to use a gutter body as the liquid transporting body, since with a gutter body, it is easy to check for the presence of pinholes in the lining layer, and hence to repair the pinholes.
In the specification of the beforementioned prior patent application, in the case where a gutter body is used as the liquid transporting body, the principle of raising the liquid with the gutter body and discharging this from the upper opening is disclosed. However there is no disclosure at all regarding the mounting face and the mounting direction.
With regards to use, in the case where the liquid discharged from the upper opening of the gutter body is used for example for washing the inner peripheral surface of the tank wall by distributing this onto the inner peripheral surface of the tank wall, or for maintaining the heat transfer area and/or washing the heat transfer surface by distributing this onto the heat transfer surface, or for evaporation by distributing this into the space above the liquid surface, then needless to say it is preferable to have a large distance and quantity (hereunder referred to as the ejection distance and ejection quantity) for the liquid ejected from the upper opening of the liquid transporting body.